Fluid heater and reactor unit



Aug. 22, 1950 1. HARTER FLUID HEATER AND REACTOR UNIT Filed April 27,1946 INVENTOR Isaac Harrier BY 7 ATTORNEY Patented Aug 22, 1950 UNITEDSTATES PATENT OFFICE FLUID HEATER AND REACTOR UNIT Application April 27,1946, Serial No. 665,417

Claims.

This invention relates in general to apparatus for the thermaldecomposition of pyrolysis of organic compounds, and more particularly,to apparatus for the thermal cracking of vaporphase hydrocarbons underrelatively low pressures and high temperatures.

The thermal cracking of vapor-phase petroleum hydrocarbons at Wpressures and high temperatures has been heretofore proposed, but suchprocesses did not survive in commercial practice because of poor heatconduction, eXces sive coke formation, and extreme sensitiveness tooperating conditions attributable in large part to the apparatus inwhich such processes were attempted.

The general object of this invention is the provision of an improvedapparatus for the thermal cracking of vapor-phase hydrocarbons atrelatively low pressures and high temperatures which are characterizedby a high rate of heat transfer to the hydrocarbon vapor being treated,low amount of coke formation, and the maintenance of stable operatingconditions throughout the operating period. A further and more specificobject is the provision of an apparatus of the character described inwhich a stream of hydrocarbon feed stock is continuously introduced intoa low pressure reaction chamber and heated to a cracking temperaturetherein by intimate contact with a circulating fluent mass of inertrefractory heat transfer material to produce a cracked gas mixturehaving a predetermined composition, while any coke or carbon residuefrom the cracking operation is continuously removed from the reactionchamher and subsequently utilized for supplying a portion of the heatrequirements of the refractory heat transfer material under eiiicientheating conditions.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawings and descriptivematter in which a preferred embodiment of the invention is illustratedand. described.

Of the drawings:

Fig. 1 is a somewhat diagrammatic elevation, partly in section, ofapparatus embodying the invention for the thermal cracking of vaporphasehydrocarbons.

2-2 of Fig. 1; and

Fig. 3 is a horizontal section taken on the line 3-..3 of Fig. 1.

While the invention in its broader aspects is adapted for the treatmentof a wide range of hydrocarbon materials, the apparatus illustrated isparticularly designed and especially adapted for the thermal treatmentof petroleum hydrocarbons, such as natural gas or gasoline, arti fi-.cial illuminating gas, gasoline vapor, oil vapor, gas oil vapor,parafiin series hydrocarbons, olefin series hydrocarbons,and cyclichydrocarbons of the naphthene and benzene series, capable of beingheat-treated to produce a cracked gas mixture.

Processes and apparatus for the pyrolysis of petroleum hydrocarbons toproduce acetylene and other gaseous compounds have been heretoforeproposed, for example, in the Hasche Pate. ents 2,236,534, 2,236,535 and2,219,679. One of the major disadvantages of such prior processes andapparatus is the difficulty of continuously heating the feed stock tothe optimum cracking temperature and of maintaining such heatingtemperatures in the reaction chamber for long peliOdS of time withoutinterrupting the operation for the elimination of carbon deposits.

In accordance with the present invention the apparatus in which thehydrocarbonaceous feed stock is treated consists of a verticallyelongated fluid heater having a substantially cylindrical fluid tightcasing ll lined with an annular wall of high temperature refractorymaterial [2. The upper end of the heater is formed by a conical plate i3also lined with high temperature refractories and having a centralheating gas outlet M controlled by a damper 55. An inlet for solid heattransfer material is arranged in one side of the plate I3, while anaccess opening ii is located at the opposite side. The in.-.

terior of the fluid heater is divided into an upper or heating chamberis in which solid heat transfer material is heated to a predeterminedtemperature and a lower or reaction chamber 2| in which thehydrocarbonaceous feed stock is sub,

jected to the desired thermal decomposition by heat absorption from theheat transfer material therein. The refractory lining !2 is shaped toprovide an inverted conical formation for both the upper chamber ill andlower chamber 2|, and an unobstructed connecting throat passage 22 ofcircular cross-section and substantially smaller diameter than theaverage diameter of either chamber Zil or 2|. The throat 22 has a slightflare downwardly to facilitate the flow of solid heat transfer materialtherethrough. The lower end of the lower chamber 2i is formed by aninverted frusto-conical screen 25 open at its lower end andconcentrically arranged with respect to a central opening 26 in theinverted conical bottom 21 of the casing The annular space between thescreen 25, casing I and bottom 2'! forms an inlet chamber 28 for thehydrocarbonaceous feed stock which is supplied thereto through a pipe 29above the upper end of the screen 25 and the lower end of a dependingannular refractory baflle 30.

In operation the chambers and 2| and throat 22 are normally filled toapproximately the levels indicated by a fluent mass or column ofincombustible refractory heat transfer material 3|, which is chemicallyinert relative to the hydrocarbonaceous feed stock. The heat transferma-- terial is supplied to the upper chamber '20 through the conduit l6and discharged from the lower chamber 2| through the opening 26. Acontinuous downward flow of the refractory material 3| through thechamber 2! throat 22 and chamber 2| is maintained by regulable transfermeans consisting of a discharge pipe 32 connecting the bottom opening tothe housing 33 of a fluid sealing variable speed rotary pocket feeder34. The feeder outlet end is connected through an expansion joint 36 andinclined conduit 31 to a box 38 opening to the lower part of an elevatorcasing 40. Openings in the box 38 permit the amount of heat transfermaterial in the system p to be increased or decreased as desired. Theelevator casing is of welded gas-tight construction and encloses anelevator 4|, shown as of a slow speed continuous bucket type, havingoverlapping buckets which are partly filled with heat transfer materialat the normal rate of material circulation. The elevator is driven by anelectric motor 42 through a speed reducer and a chain and sprocketconnection to the elevator head shaft. The elevator buckets empty into adischarge pipe 44 having a lower side outlet 45. The outlet 45 isconnected to an inclined pipe 48, an expansion joint 49, and opens tothe inlet pipe It. With this arrangement a continuous circulation ofrefractory heat transfer material can be maintained externally of thefluid heater between the discharge opening 26 and inlet pipe H5, so thatthe mass or column of heat transfer material within the chambers '20 and2|, and throat 22, will descend at a predetermined rate, dependent uponthe speed of the feeder 34 and elevator 4|.

A relatively wide range of refractory materials can be used as the heattransfer material 3|, the material chosen depending upon the particularoperating conditions to be maintained in the unit. The material selectedshould have a high strength, hardness, resistance to thermal shock, andresistance to fusing together at high temperatures. Such materials maybe ceramic refractories or corrosion resistant alloys and alloy steels,in small pieces of regular or irregular shape, such as sized grog,pebbles, or crystals of mullite, silicon carbide, alumina, or otherrefractories. As disclosed in a copending application of E. G. Bafleyand R. M. Hardgrove, Serial No. 502,580, now Patent No. 2,447,305,substantially spherical pellets of uniform shape and size in the rangeof to 1" in diameter and formed of a mixture of calcined Georgia kaolin,raw Georgia kaolin, and a binder, fired to 2850-3000 F., have beensuccessfully used. The pellet size is generally a compromise between adiameter small enough to minimize thermal shocks, impact forces, and toprovide a large heat transfer surface, and a diameter large enough foreconomical manufacture, and to withstand the desired gas velocitieswithout lifting. Pellets of inch and 1% inch diameter have been foundsuitable.

When the apparatus of the present invention is used in the manufactureof acetylene for example, a hydrocarbon feed stock such as naturalgasoline, which is a mixture of paraflin hydrocarbons containing five ormore hydrocarbons, mixed with steam is continuously introduced at a lowtemperature and a pressure slightly above atmospheric into the annularinlet chamber 28 through the conduit 29, the vapor mixture entering thelower chamber 2| throughout the height and circumference of the screen25. The chamher 2| is proportioned in height, flow area, and

volume and a pellet size selected to permit a very rapid passage of thehydrocarbonaceous vapor upwardly through the interstices in thedescending mass of highly heated refractory pellets 3'2. The intimatecontact between the ascending vapor and descending mass of heat transfermaterial causes the vapor to be heated to a cracking temperature beforereaching the upper end of the mass in the chamber 2| and cracking of thevapor occurs in the upper part of the mass. A rapid quenching of thegaseous end products to a temperature at which acetylene is stable isessential and this is effected by the arrangement of a circular seriesof gas outlets in the upper end of the chamber 2| above the level of thelower end of the throat '22 and the location of a heat exchanger havinga high rate of heat absorption in each outlet 50. In the apparatusillustrated, each heat exchanger consists of an inclined cylindricaldrum 5| having a downwardly dished tube sheet 52 at its upper and lowerends connected by tubes 53 through which the outgoing gases flow. A heatabsorbing fluid, preferably water, is supplied to the lower end of eachdrum 5| through a pipe 54 connected to an annular supply pipe 55.

The steam generated in each drum is withdrawn through a pipe 55connected to an annular steam main 5'! leading to a point of use, suchas the diluent steam supplied to the vapor inlet pipe 29. The upper endof each drum is closed by a plate 58 to which a gas outlet pipe 59 isconnected for delivering the cooled cracked gas mixture to an annularduct 60. The cooled gas mixture is then scrubbed to eliminate tar andoil particles in suspension, and then treated in a well known manner toseparate into acetylene, ethylene, and fuel gas fractions.

The refractory pellets are heated to the desired temperature while inthe upper chamber 20 by utilizing a portion of the fuel gases generatedin the lower chamber 2!. For this purpose a circular series ofsymmetrically arranged downwardly inclined ports 62 are formed in theside wall of the chamber 20 intermediate the height thereof and thesuperjacent portion of the wall arranged to form an annular downwardlyinclined baffle 63 overlapping the inner ends of the ports 62, and thuspreventing the entrance thereto of the refractory pellets. An annularwind box 64 having one or more air inlet connections 65 thereto, opensto the outer end of the ports 62. Fuel gas is supplied to the ports 62through valve controlled pipes 66 projecting downwardly from an annularsupply duct 61 through the wind box 64 into the outer portion of theports 62. With this arrangement a combustible mixture of fuel and air,initially ignited in any suitable manner, is supplied to the ports 62and the pellet mass in the chamber 20 is heated by the resulting seriesof symmetrically arranged flames impinging on the pellets intermediatethe height of the chamber 20. The heating gases thus generateddistribute substantially uniformly throughout the pellet mass and flowupwardly through the inter stices therein in intimate contact with thedescending pellets. The heating gases flow out of the chamber throughthe gas outlet M, with the gas outflow regulated by the damper l5 tocontrol the pressure in the chamber 20. The relative pressures in thechambers 20 and 2'! can be advantageously regulated to provide zero or adownward or upward gas flow through the throat 22 by regulating theoperation of damper l5 by control mechanism responsive to the pressuredifferential across the throat 22, as disclosed and claimed in saidcopending application of E. G. Bailey and R. M. Hardgrove, Serial No.502,580. To facilitate this result, the. throat 22 is preferably madewith the smallest diameter which will permit the pellets to flowtherethrough without danger of bridging over therein, and pressure tapsI0 and H are arranged in the lower part of the chamber 20 and upper partof the chamber 2! respectively, to measure the pressure differentialacross the throat. Separation of the gases in the upper and lowerchambers can be further insured by the introduction of an inert sealinggas, such as steam, into the throat through a valve controlled pipe 13.

In addition to the control provisions described, the supplies of steamand hydrocarbonaceous vapor to the lower chamber and of fuel gas and airto the upper chamber are manually or' automatically regulated in anysuitable manner. These controls in conjunction with therpressuredifferential and pellet circulation controls described facilitate themaintenance'of optimum operating conditions in the unit.

Representative operating conditions for the pyrolysis of naturalgasoline involve the introduction of a. mixture of natural gasoline andsteam diluent, in the proportions of approximately gasoline and 70%steam, at a temperature of 250 F. and a pressure of 3 p. s. i.. into thelower part of the'pellet mass in the chamber 2|. The chamber 2| isproportioned to provide a pressure drop of 1 p. s. i.. and av time oftravel. of 0.1 second of the vapor mixture through the lower chamber.The pellets enter the upper chamber 20 at a. temperature of 550 F. andare heated therein to a temperature of 2700 F. Under these conditionsthe hydrocarbonaceous feed stock will be rapidly heated to a maximumtemperature of about 2380 F. in the lower chamber, which isapproximately the optimum crackin temperature for the pyrolysis ofnatural gasoline. The pellet temperature in the upper. part of the lowerchamber is sufficiently high 'to maintain the hydrocarbonaceous vapor atthe desired cracking temperature for the short time necessary (less than0.1 sec.) to produce a cracked gas mixture having a high yield ofacetylene. The intimate contact of hydrocarbons with a high temperaturemass of refractory material has been found to facilitate the crackingoperation, and consequently the formation of acetylene. The cracked gasmixture is cooled in about 0.03 second to a temperature of 750 F., atwhich acetylene will be stable. The heating gases enter the upperchamber at a temperature of about 2900 F. and leave through the outletI4 at 750 F. Any carbon deposition on the pellets while in the crackingzone of the lower chamber will pass with the pellets to the elevator andbe burned off on their return to the upper chamber 20 thereby providingpart of the heat requirements in that chamber. A constant circulation ofpellets through the unit is maintained at a rate of approximately 12cycles per hour.

When the apparatus of this invention. is used and the describedoperating conditions are adhered to a gaseous end product of uniformcomposition can be continuously maintained. A high yield of acetylene isproduced together with an amount of fuel gases more than sumcient tosupply the heat requirements of the unit. The. inverted conicalformation of the chambers 20 and 2| is particularly advantageous,insuring a. substantially uniform distribution of the fluids introducedat the narrowed cross-section thereof and minimizing the pellet liftingeffect of the ascending gas streams by the progressively increasing flowareas available. The rapid quenching of the cracked gaseous mixture bythe heat exchangers as the gases leave the reaction chamber facilitatesthe control of the time of heat treatment and this makes it possible toa large extent to prevent deleterious overcracking of the resultant gasmixture. The substantial heat recovery by the heat exchange units incooling the outgoing cracked gas mixture also provides a practicableoverall thermal efiiciency.

In view of the foregoing examples of particular applications of theapparatus of this invention to a specific process, it will be obvious tothose skilled in the art that the apparatus is adapted for thecontinuous thermal decomposition of a wide range of fluid hydrocarbonsunder uniform operating conditions, the contact time, reactiontemperature and degree of quench being controlled in each case to securethe optimum end product.

While in accordance with the provisions of the statutes I haveillustrated and described herein the best form of the invention known tome. those skilled in the art will understand that changes may be made inthe form of the apparatus disclosed without departing from the spirit ofthe invention covered by the claims, and that certain features of myinvention may sometimes be used to advantage without a corresponding useof other features.

What is claimed is:

l. A fluid heater comprising an upper chamber having a solid materialinlet and a heating gas outlet at its upper end and a solid materialoutlet at its lower end, a lower chamber having a solid material outletand a gaseous fluid inlet at its lower end and a plurality ofcircumferentially equally spaced gaseous fluid outlets at its upper end,a throat passage of substantially reduced cross-section merging withsaid upper chamber material outlet and projecting into the upper endportion of said lower chamber, a feeder arranged to regulate agravitational movement of a cont nuous mass of gas-pervious refractoryheat transfer material downwardly through said upper chamber, throat andlower chamber, a conveyor arranged to receive heat transfer materialfrom said feeder for delivery to the solid material inletv at the upperend of said upper chamber, means for heating said heat transfer materialwhile in said upper chamber. and an indirect contact heat exchangeropening directly into each of said lower chamber fluid outlets to quenchthe hot gaseous fluid leaving said lower chamber by heat exchange with avaporizable medium.

2. A fluid heater comprising walls defining an upper heating chamberhaving a solid material inlet and a heating gas outlet inits upper end,

an inverted frusto-conical lower end portion of said walls defining adownwardly tapered portion of said chamber ending in a verticallyelongated throat passage, plurality of circumferen tially spaced fuelburners arranged for the introduction of heating gas into said upperchamber at a position intermediate its height for upward flowtherethrough to said heating gas outlet, walls defining a lower chamberof downwardlytapering circular cross-section having a solid materialoutlet and a gaseous fluid inlet in its lower end portion, the upperWall portion of said lower chamber encircling the lower end portion ofthe inverted frusto-conical wall of said. upper chamher in radiallyspaced relationship, a feeder arranged to regulate the gravitationalmovement of a continuous mass of gas-pervious solid heat transfermaterial downwardly through said upper chamber, throat and lowerchamber, and a plurality of circumferentially equally spaced tubularheat exchange units positioned alongside the tapered wall of said upperchamber with the lower end of each unit opening directly into theannular space between the exterior surface of the wall defining saidthroat passage and the interior surface of the upper end portion of saidlower chamber wall to receive the gaseous fiuid passed upwardly throughthe lower chamber from said gaseous fluid inlet. 7 3. A fluid heatercomprising walls defining an upper chamber of downwardly taperingcircular cross-section substantially throughout its height and having asolid material inlet and a heating gas outlet at its upper end and asolid material outlet at its lower end, walls defining a lower chamberof downwardly tapering circular crosssection substantially throughoutits height and having a solid material outlet and a gaseous fluid inletat its lower end, a throat passage of substantially reducedcross-section merging with said upper chamber material outlet andprojecting into said lower chamber to define an annular gaseous fluidoutlet between the exterior wall of the throat and the upper portion ofsaid lower chamber wall, a feeder arranged to regulate a gravitationalmovement of a continuous mass of gaspervious refractory heat transfermaterial downwardly through said upper chamber, throat and lowerchamber, a, conveyor arranged to receive heat transfer material fromsaid feeder for delivery to the solid material inlet at the upper end ofsaid upper chamber, a plurality of circumferentially spaced fuel burnersarranged for introducing heating gases into said upper chamher at aposition intermediate its height for upward flow therethrough in directcontact heat transfer relation with the mass of gas-pervious heattransfer material therein, and a plurality of circumferentially spacedtubular heat exchangers opening into said lower chamber gaseous fluidoutlet and arranged to quench the hot gaseous fluid leaving said lowerchamber. 4. A fluid heater comprising walls defining an upper heatingchamber having a solid material inlet and a heating gas outlet in itsupper end, an inverted frusto-conical lower end portion of said walldefining a downwardly tapered lower end portion of said chamber endingin a vertically elongated throat passage of substantially forupward'fiow therethrough to said heating gas outlet, walls defining alower chamber of downwardly tapering circular cross-section having asolid material outlet and a gaseous fluid inlet in its lower endportion, the upper wall portion of said lower chamber encircling thelower end portion of the inverted frusto-conical wall of said upperchamber in radially spaced relationship,- a feeder arranged to regulatethe gravitational movement of a continuous mass of gas-pervious solidheat transfer material downwardly through said upper chamber, throat andlower chamber,- and a plurality of circumferentially equally spacedtubular heat exchange units positioned alongside the tapered wall ofsaid upper chamber: with the lower end of each unit opening directlyinto the'annular space between the exterior surface of the wall definingsaid throat passage and the interior surface of the upper end portion ofsaid lower chamber wall to receive the gaseous fluid passed upwardlythrough the lower chamberfrom said gaseous fluid inlet, each of saidheat exchange units having a cross-sectional dimension substantiallyequal to the radial dimension between said throat and lower chamberwalls.

'5. In a heat exchange device of the general type-having an upperchamber enclosing an inert fluent gas-pervious mass of solid heattransfer material, a'lower chamberenclosing a mass of such material, apassage forming a throat between said upper and lower chambers and en-'closing a mass of such material connecting said material masses, meansexternal of said chambers and throat to return the material from an exitin the lower chamber to an inlet to the upper chamber, means for heatingthe material in the upper chamber by direct contact countercurrentrelationship with a heating gas, means for heating a fluid to be' heatedby'direct contact counter-' current relationship with the heatedmaterial within said lower chamber, the lower end portion of said throatcooperating with the upper end portion of said lower chamber to definean annu lar heated fluid outlet chamber, the improvement comprising aplurality of tubular vapor generat-' ing heat exchange unitscircumferentiall'y equally spaced about said upper chamber and throatpassage with the heated 'fluid entrance end of each unit openingdirectly into said annular heated fluid outlet chamber at positionssubstantially equally spaced from the upper'sur face of the refractoryheat transfer material within said lower chamber.

' ISAAC HARTER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATJ s

1. A FLUID HEATER COMPRISING AN UPPER CHAMBER HAVING A SOLID MATERIALINLET AND A HEATING GAS OUTLET AT ITS UPPER END AND A SOLID MATERIALOUTLET AT ITS LOWER END, A LOWER CHAMBER HAVING A SOLID MATERIAL OUTLETAND A GASEOUS FLUID INLET AT ITS LOWER END AND PLURALITY OFCIRCUMFERENTIALLY EQUALLY SPACED GASEOUS FLUID OUTLETS AT ITS UPPER END,A THROAT PASSAGE OF SUBSTANTIALLY REDUCED CROSS-SECTION MERGING WITHSAID UPPER CHAMBER MATERIAL OUTLET AND PROJECTING INTO THE UPPER ENDPORTION OF SAID LOWER CHAMBER, A FEEDER ARRANGED TO REGULATEAGRAVITATIONAL MOVEMENT OF A CONTINUOUS MASS OF GAS-PERVIOUS REFRACTORYHEAT TRANSFER MATERIAL DOWNWARDLY THROUGH SAID UPPER CHAMBER, THROAT ANDLOWER CHAMBER, A CONVEYOR ARRANGED TO RECEIVE HEAT TRANSFER MATERIALFROM SAID FEEDER FOR DELIVERY TO THE SOLID MATERIAL INLET AT THE UPPEREND OF SAID UPPER CHAMBER, MEANS FOR HEATING SAID HEAT TRANSFER MATERIALWHILE IN SAID UPPER CHAMBER, AND AN INDIRECT CONTACT HEAT EXCHANGEROPENING DIRECTLY INTO EACH OF SAID LOWER CHAMBER FLUID OUTLETS TO QUENCHTHE HOT GASEOUS FLUID LEAVING SAID LOWER CHAMBER BY HEAT EXCHANGE WITH AVAPORIAZABLE MEDIUM.